The present invention relates to the fields of surgical sutures and local anesthetics, and more particularly to the field of surgical sutures that contain a local anesthetic, which is released from the sutures to relieve post-operative pain.
Prior to the closure of an incision in surgery, a local anesthetic is usually injected into the operative site to relieve post-operative pain. The effective duration of the surgically-applied local anesthetic is, however, quite limited, often less than six hours. After the surgically-applied local anesthetic becomes ineffective, a narcotic analgesic which acts on the central nervous system, such as morphine, must be administered to the patient. But narcotic analgesics have adverse side effects, including loss of alertness, respiratory complications, nausea, and possible addiction.
It is therefore desirable to minimize the use of narcotic analgesics to treat post-operative pain. One method of doing this is to incorporate a local anesthetic into the surgical sutures used at the operative site. In this way, the local anesthetic can be released over a longer duration as the suture material dissolves and is absorbed by the surrounding tissue. It is also desirable to have a method of regulating the dosage and release rate of the anesthetic from the suture, since different surgical procedures will require varying degrees and durations of post-operative pain relief.
One approach to anesthetic sutures is to provide an “active suture”, where the suture is hollow and is connected to an external anesthetic delivery device, such as an injection pump, a syringe, or an IV. Examples of such “active sutures” are disclosed in the U.S. patents of Nakao (U.S. Pat. No. 5,458,582) and Cichocki, Jr. (U.S. Pat. No. 8,257,393). While the rate and duration of drug administration is controllable using these devices, that control requires active intervention of a medical professional, and end portions of the sutures must be left protruding from the operative site.
Another approach is to provide an anesthetic coating on the sutures, so that the local anesthetic leaches over time into the operative site. Examples of coated sutures are taught in the U.S. patents of Skiba (U.S. Pat. No. 6,689,153) and Cohan (U.S. Pat. No. 8,273,104), and in the U.S. patent applications of Shibuya (2002/0055759) and Balar et al. (2006/0182778). But these uniformly coated sutures lack any mechanism for controlling the rate at which the anesthetic is released and the duration of the release.
The present invention, on the other hand uses a differentially coated/impregnated multifilament or braided filament suture material to adjust the time-release period and the rate of anesthetic release to suit the needs of the specific patient and/or the nature of the surgical procedure.